Pedogenesis--A Major Diagenetic Process in Giant Hugoton Gas Field

Dennis R. Prezbindowski, Mary L. Passaretti, Gayle S. Tapp

Pedogenic processes (soil forming) played an important role in the depositional and diagenetic evolution of the giant Hugoton gas field. The major reservoir facies are developed in the Permian Chase Group of Kansas, Oklahoma, and Texas. The Chase Group is approximately 300 ft thick in the Texas County area of Oklahoma and consists of four shallowing-upward carbonate cycles. The middle two cycles, the Towanda and Gage Members, and the Winfield and Odell formations are capped by the well-developed paleosol deposits of the Gage and Odell. These paleosols are developed over a 7,500-mi² area. The maximum thicknesses are found along the western and northern limits of the Hugoton field with gradual thinning to the south and east. Facies succession, color changes, late al continuity, karst features developed in the underlying carbonates, caliche horizons, petrographic textures, and stable isotopic data support a pedogenic origin.

The Gage and Odell paleosols are characterized by compound soil profiles with a lower, greenish hydromorphic soil zone capped by reddish-brown aridisols containing multiple caliche horizons. The maturity of the caliche horizons indicates that several hiatuses (on the order of tens of thousands of years) occurred during soil accretion. These paleosols served as regional surfaces for the introduction of meteoric water charged with CO₂ and organic acids produced in the soil zones. This fluid influx caused extensive dissolution of anhydrite, calcite, and dolomite in the underlying supratidal to subtidal carbonate sediments. This early development of secondary porosity was important to establishing the reservoir quality of the Chase Group carbonates.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.